What you can do is drag the folders from Mac Outlook into the desktop. There’s a third choice which might work in case you have only a couple of folders. So, you cannot go the conventional route of using the data files, leaving you the only choice of converting OLM to Mac Mail. Mac Mail only allows importing MBOX files and Outlook only exports data to OLM files. The reason why you need a third-party converter is that both clients offer no official import/export feature to get it done. Jumping ship from Outlook to Mac Mail? You are going to need an Outlook OLM to Mac Mail converter that can help you move your data emails, contacts, and calendar.